High performance and low cost are often the main driving forces for determining whether a particular technology will enjoy widespread adoption. Over the past few years, superlattice (SL) technology operating in the mid- and long-wavelength infrared has progressed significantly, demonstrating the potential for realization of high performance infrared sensor materials. In particular, the type II SL material system has been identified as particularly promising for infrared detection as its cut-off wavelength can span a broad spectrum from mid-wavelength infrared (MWIR) to very long-wavelength infrared (VLWIR) (3 μm<λ<30 μm) by engineering the layer thicknesses. The major advantage of the SL material for IR detection applications is that it is a mechanically robust III-V material platform, which offers all the advantages of the III-V material system and is capable of normal incidence absorption, and therefore has high quantum efficiency.
More recently, barrier infrared detector (BIRD) designs such as the nBn device design (Maimon and Wicks, Appl. Phys. Lett., vol. 89, no. 15, p. 151109, 2006, the disclosure of which is incorporated herein by reference) have enhanced the performance of superlattices in the MWIR region by reducing the Shockley-Read-Hall (SRH) associated dark currents. Elaboration of these nBn design have shown the superiority of these barrier devices for MWIR (U.S. Pat. No. 8,217,480 B2, the disclosure of which is incorporated herein by reference), and LWIR (Ting et al., Appl. Phys. Lett. 95, 023508 (2009), the disclosure of which is incorporated herein by reference).
Despite the promise offered by SL technology and BIRD device designs barrier infrared detectors configured to operate in the long-wave infrared regime are challenging to form.